Sen. Ted Cruz on Thursday addressed criticism that he is supporting insurgent Republican candidates targeting incumbents in primaries, saying his goal is to stay out of the races, but it’s not “ironclad.”

POLITICO chief White House correspondent Mike Allen asked Cruz to respond to a POLITICO report Wednesday that he had signed a letter for an outside funding group challenging Republican incumbents, something he reportedly had pledged not to do.

“I thought that story, to be honest, was pretty silly,” Cruz said at POLITICO’s Playbook Breakfast on Thursday. “That particular letter was a letter I signed last April, nearly a year old. I didn’t even know the group had sent the letter out again.”

The Texas Republican said the story line in the media of him not playing nice with Republican colleagues was sensationalized, to an extent.

“You don’t have to search hard to find colleagues of mine saying some very nasty things about me,” Cruz said. “I can’t control what they do, but I can control what I do, and I have not reciprocated and I don’t intend to.”

Cruz said in the case of the letter, he wasn’t breaking any pledges.

“It was a letter I had signed before they’d endorsed anyone in primaries,” Cruz said. “What I’ve said is, I’m likely going to stay out of incumbent Republican primaries. So last April, I signed a letter for that group, and that group supported me in my race.”

But Cruz said he had made “no such ironclad promise” to avoid groups targeting sitting senators.

“What I have said is that I’m likely going to stay out of incumbent Republican primaries,” he said again, saying he didn’t put anything in “concrete … because things can change in politics.”

As for the high-profile primary in his own state of Texas next month, where Rep. Steve Stockman is challenging incumbent Sen. John Cornyn in the GOP primary, Cruz said his vote is “between me and the ballot box.”

“As I’ve said, I’m going to likely stay out of incumbent Republican primaries; that is an incumbent Republican primary,” Cruz said, declining to endorse Cornyn. “I like John Cornyn, he and I have worked together very closely, we’ve agreed on the vast majority of things. There are some areas in which we’ve disagreed.”

“I trust the grass roots,” Cruz said. “An incumbent has enormous advantages. It ain’t that hard for an incumbent senator to get reelected, and, you know, if an incumbent needs my help to hold onto their seat, there’s something really wrong that’s happened with the grass-roots voters back home.”